The subject matter disclosed herein relates to a valve system, and more specifically to a valve system having a valve seat with a crenulated portion that orients flow in a generally circumferential direction.
Operation of a steam turbine may require application of valves that control steam flow upstream of machinery. Typically, there are two types of main valves that control and protect a turbine, control valves and stop valves. Modern steam turbines typically employ valves that are combined control and stop valves, which operate in not only an open and closed mode, but also in intermediate positions as well. Combined control and stop valve includes a control valve having a control valve disk, and a stop valve having a stop valve stem and a stop valve disk. Both valves are assembled in one common pressure vessel and may share one seat. The control valve disk is positioned in relation to a valve seat, and is actuated to modulate flow. The stop valve is situated within an opening located in the valve seat and is typically actuated in some situations to generally prevent turbine overspeed. In one example, the valve seat may include a crenulated portion where flow is split into small jets in an effort to reduce large pressure fluctuations as the control valve disk is actuated.
Solid Particle Erosion (SPE) occurs within a steam turbine when solid particles are exfoliated off of steam turbine components such as, for example, boiler tubes and steam leads. The exfoliated particles become entrained in the steam flow path. The particles are carried by high velocity flow paths located within the steam turbine. These flow paths may cause the particles to impinge against components located within the steam turbine at a relatively high velocity. For example, the particles may impinge against the stop valve stem located within the valve seat of the combined control and stop valve. The issue of particle impingement against the stop valve stem is further compounded with the fact that the valve seat tends to have geometry that directs the particles towards the stop valve stem.